Carbon Nano Tubes: Synthesis and Characterization for Microwave Applications
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Transactions on Electrical and Electronic Materials https://doi.org/10.1007/s42341-020-00260-6
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Carbon Nano Tubes: Synthesis and Characterization for Microwave Applications Vikas Kumar1 Received: 20 October 2019 / Revised: 29 October 2020 / Accepted: 4 November 2020 © The Korean Institute of Electrical and Electronic Material Engineers 2020
Abstract Attenuators are used to suppress the reflections in the helix traveling wave tubes and these attenuators are normally fabricated with the coating of some lossy material on the helix support rods. Carbon is the most commonly used attenuator material for the microwave applications and is usually deposited by pyrolytic or sputtering methods. However, other materials like iron and nickel are also used sometime for the attenuation applications. Helix is usually supported by the rods of some ceramic material like APBN (Anisotropic Pyrolytically Deposited Boron Nitride) or Alumina etc. Attenuator materials are deposited on these support rods to absorb the reflections. In order to look forward to new methods of deposition as well new attenuator materials, Carbon nanotubes have been proposed as another alternative attenuator material. Multi-Wall Cabon Nano-Tubes have been grown on the rectangular alumina substrate using the chemical vapour deposition method. Microwave attenuation/loss has been measured on these samples with X-band microwave frequencies. Specific experimental set-up has been designed for the measurement. The work is centered toward making good quality novel attenuators for the microwave applications and particularly the TWT. Keywords Traveling wave tube · Loss measurements · Nanotubes
1 Introduction In a large number of high power communication systems, Traveling wave tube (TWT) is employed as an amplifier for the high gain, broadband microwave applications [1–3]. Major applications of TWT include the domains of satellite communication and warfare systems. Although there are two broad categories of TWT (Coupled Cavity TWT and Helix TWT), present work is concerned with the Helix TWT. Continuous interaction between the electric field and electron beam is the primary method of amplification in this TWT. A special type of RF circuit known as the slow wave structure (SWS) is employed for this purpose. Helix is commonly used SWS for extremely wide-band applications [4]. Considering the space application, stability of the traveling wave amplifier [5–7], during the lifetime of operation is very much critical and becomes a dominant factor for it design and fabrication. The major factors, which can reduce the * Vikas Kumar [email protected] 1
Chaudhary Bansi Lal University, Bhiwani, Haryana 127021, India
stability of the device include reflections, backward wave oscillations, band-edge oscillations and generation of higher order spurious modes. These effects can limit the usefulness of the devise for any critical applications. Reflections may be present in device due to any mismatch at the input or output ends in the tube and the presence of
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